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Солдатов, Алексей Анатольевич

Организационные подразделения

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Цель ИЯФиТ и стратегия развития - создание и развитие научно-образовательного центра мирового уровня в области ядерной физики и технологий, радиационного материаловедения, физики элементарных частиц, астрофизики и космофизики.

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Солдатов

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Алексей Анатольевич

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Particle Polarization and Structure of Vortical Field in Relativistic Heavy-Ion Collisions
(2020) Toneev, V. D.; Ivanov, Y. B.; Soldatov, A. A.; Солдатов, Алексей Анатольевич
© 2020 Published under licence by IOP Publishing Ltd.We review studies of vortical motion and the resulting global polarization of Λ and Λ hyperons in heavy-ion collisions within 3FD model. The 3FD simulations indicate that energy dependence of the observed global polarization of hyperons in the midrapidity region is a consequence of the decrease of the vorticity in the central region with the collision energy rise because of pushing out the vorticity field into the fragmentation regions. At high collision energies this pushing-out results in a peculiar vortical structure consisting of two vortex rings: One ring in the target fragmentation region and another one in the projectile fragmentation region with matter rotation being opposite in these two rings.
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Equilibration and baryon densities attainable in relativistic heavy-ion collisions
(2020) Ivanov, Y. B.; Soldatov, A. A.; Солдатов, Алексей Анатольевич
Kinetic equilibration of the matter and baryon densities attained in the central region of colliding Au+Au nuclei in the energy range of root s(NN) = 3.3-39 GeV are examined within the model of three-fluid dynamics. It is found that the kinetic equilibration is faster at higher collision energies: the equilibration time (in the center-of-mass frame of colliding nuclei) rises from approximate to 5 fm/c at root s(NN) = 3.3 GeV to approximate to 1 fm/c at 39 GeV. The chemical equilibration, and thus thermalization, takes longer. We argue that the presented time evolution of the net-baryon and energy densities in the central region is a necessary prerequisite of proper reproduction of bulk observables in midrapidity. We suggest that for informative comparison of predictions of different models it is useful to calculate an invariant four-volume (V-4), where the proper density of the equilibrated matter exceeds a certain value. The advantage of this four-volume is that it does not depend on specific choice of the three-volume in different studies and takes into account the lifetime of the high-density region, which also matters. The four-volume V-4 = 100 fm(4)/c is chosen to compare the baryon densities attainable at different energies. It is found that the highest proper baryon density increases with the collision energy rise, from n(B)/n(0) approximate to 4 at 3.3 GeV to n(B)/n(0) approximate to 30 at 39 GeV. These highest densities are achieved in the central region of the colliding system.
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Correlation between global polarization, angular momentum, and flow in heavy-ion collisions
(2020) Ivanov, Y. B.; Soldatov, A. A.; Солдатов, Алексей Анатольевич
Possible correlations of the global polarization of A hyperons with angular momentum and transverse flow in the central region of colliding nuclei are studied based on a refined estimate of the global polarization. Simulations of Au + Au collisions at collision energies root s(NN )= 6-40 GeV are performed within the model of the three-fluid dynamics. Within the crossover and first-order-phase-transition scenarios this refined estimate quite satisfactorily reproduces the experimental STAR data. Hadronic scenario fails at high collision energies, root s(NN ) > 10 GeV, and even predicts the opposite sign of the global polarization. It is found that the global polarization correlates with neither the angular momentum accumulated in the central region nor with directed and elliptic flow. At the same time we observed correlation between the angular momentum and directed flow in both their time and collision-energy dependence. These results suggest that, although initially the angular momentum is the driving force for the vortex generation, later the angular momentum and vortex motion become decorrelated in the midrapidity region. Then the midrapidity angular momentum is determined by the pattern of the directed flow and even becomes negative when the antiflow occurs. At the freeze-out stage, the dominant part of the participant angular momentum is accumulated in the fragmentation regions.
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Vorticity and Particle Polarization in Relativistic Heavy-Ion Collisions
(2020) Toneev, V. D.; Ivanov, Y. B.; Soldatov, A. A.; Солдатов, Алексей Анатольевич
© 2020, Pleiades Publishing, Ltd.Abstract: We review studies of vortical motion and the resulting global polarization of (Formula presented.) and (Formula presented.) hyperons in heavy-ion collisions, in particular, within 3FD model. 3FD predictions for the global midrapidity polarization in the FAIR-NICA energy range are presented. The 3FD simulations indicate that energy dependence of the observed global polarization of hyperons in the midrapidity region is a consequence of the decrease of the vorticity in the central region with the collision energy rise because of pushing out the vorticity field into the fragmentation regions. At high collision energies this pushing-out results in a peculiar vortical structure consisting of two vortex rings: one ring in the target fragmentation region and another one in the projectile fragmentation region with matter rotation being opposite in these two rings.
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Estimates of hyperon polarization in heavy-ion collisions at collision energies sNN =4-40 GeV
(2019) Toneev, V. D.; Ivanov, Y. B.; Soldatov, A. A.; Солдатов, Алексей Анатольевич
© 2019 American Physical Society.Global polarization of Λ and Λ hyperons in Au+Au collisions at collision energies sNN=4-40GeV in the midrapidity region and total polarization, i.e., averaged over all rapidities, are studied within the scope of the thermodynamical approach. The relevant vorticity is simulated within the model of the three-fluid dynamics (3FD). It is found that the performed rough estimate of the global midrapidity polarization quite satisfactorily reproduces the experimental STAR data on the polarization, especially its collision-energy dependence. The total polarization increases with the collision energy rise, which is in contrast to the decrease of the midrapidity polarization. This suggests that at high collision energies the polarization reaches high values in fragmentation regions.
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On Ambiguity of Definition of Shear and Spin-Hall Contributions to Λ Polarization in Heavy-Ion Collisions
(2022) Ivanov, Y. B.; Soldatov, A. A.; Солдатов, Алексей Анатольевич
Recently proposed thermal-shear and spin-Hall contributions to the particle polarization in heavy-ion collisions are discussed. Alternative definitions of the thermal-shear contribution, i.e. those of Becattini–Buzzegoli–Palermo on the one hand and Liu–Yin on the other, are very similar in the midrapidity region while quite different at forward-backward rapidities, which are measured in fixed-target experiments. It is shown that the thermal-shear contribution to the global polarization with momentum averaging extended to all momenta is very different within these alternative definitions. The spin-Hall contribution to the global polarization, defined similarly to the Liu–Yin shear one, is identically zero, if averaging runs over all momenta. Only application of restrictive momentum acceptance and the boost (to Λ rest frame) correction result in nonzero global spin-Hall polarization. If the spin-Hall contribution were defined similarly to Becattini–Buzzegoli–Palermo shear one, the global spin-Hall polarization would be non-zero even without any acceptance and the boost correction. © 2022, Pleiades Publishing, Inc.
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Global Λ polarization in heavy-ion collisions at energies 2.4-7.7 GeV: Effect of meson-field interaction
(2022) Ivanov, Y. B.; Soldatov, A. A.; Солдатов, Алексей Анатольевич
© 2022 American Physical Society.Based on the three-fluid model, the global Λ polarization in Au+Au collisions at 2.4 ≤sNN≤ 7.7 GeV is calculated, including its rapidity and centrality dependence. Contributions from the thermal vorticity and meson-field term (proposed by Csernai, Kapusta, and Welle) to the global polarization are considered. The results are compared with data from recent and ongoing STAR and HADES experiments. It is predicted that the polarization maximum is reached at sNN≈3 GeV, if the measurements are performed with the same acceptance. The value of the polarization is very sensitive to interplay of the aforementioned contributions. In particular, the thermal vorticity results in quite strong increase of the polarization from the midrapidity to forward/backward rapidities, while the meson-field contribution considerably flattens the rapidity dependence. The polarization turns out to be very sensitive to details of the equation of state. While collision dynamics become less equilibrium with decreasing collision energy, the present approach to polarization is based on the assumption of thermal equilibrium. It is found that equilibrium is achieved at the freeze-out stage, but this equilibration takes longer at moderately relativistic energies.
Открытый доступ
Λ Polarization and Vortex Rings in Heavy-Ion Collisions at NICA Energies
(2023) Ivanov, Y. B.; Soldatov, A. A.; Солдатов, Алексей Анатольевич
We review recent studies of vortical motion and the resulting polarization of О› hyperons in heavy-ion collisions at NICA energies, in particular, within the model of three-fluid dynamics (3FD). This includes predictions of the global О› polarization and ring structures that appear in Au+Au collisions. The global О› polarization in Au+Au collisions is calculated, including its rapidity and centrality dependence. The contributions of the thermal vorticity and meson-field term (proposed by Csernai, Kapusta, and Welle) to the global polarization are considered. The results are compared with data from recent STAR and HADES experiments. It is predicted that the polarization maximum is reached at sNNв‰€ 3 GeV if the measurements are performed with the same acceptance. It is demonstrated that a pair of vortex rings are formed, one at forward rapidities and another at backward rapidities, in ultra-central Au+Au collisions at sNNandgt; 4 GeV. The vortex rings carry information about the early stage of the collision, in particular, the stopping of baryons. It is shown that these rings can be detected by measuring the ring observable RО›, even in the midrapidity region at sNN= 5вЂ“20 GeV. At forward/backward rapidities, the RО› signal is expected to be stronger. The possibility of observing the vortex-ring signal against the background of non-collective transverse polarization is discussed.